Friday, October 23, 2009

Ovulation and The Menstrual Cycle

Ovulation and the Menstrual Cycle

The onset of menstrual flow (menses) generally marks the beginning of the female reproductive cycle, during which an egg is matured and the uterine lining (endometrium) develops, to allow for embryo implantation and the development of a normal pregnancy. If no pregnancy occurs, then the endometrial lining is shed (the menstrual flow begins) and the cycle begins once again. Normally, menstrual cycle intervals are about every 28-30 days. Many fertile women have somewhat longer or shorter menstrual cycle intervals, suggesting that the egg quality at full maturity is somewhat independent of the time taken for the egg to develop fully.

The initial part of the menstrual cycle is often thought of as the “egg development” phase, and since the eggs develop within ovarian cysts called follicles this is usually referred to as the “follicular phase.” Ovulation normally occurs once a mature egg is developed. The final part of the menstrual cycle is the “luteal phase” marked by elevated progesterone production. The progesterone appears to modify the endometrium within the uterine cavity to allow for a 4-5 day “window of uterine receptivity” for embryo implantation, and if no pregnancy develops then the entire lining is shed about 14 days after ovulation. If a pregnancy does develop, then progesterone production normally remains elevated throughout the course of the pregnancy.

There are some problems with ovulation that can reduce fertility. Hormone imbalances involving thyroid hormone or prolactin can interfere with ovulation. If the egg is released from a follicle that has a smaller diameter than usual, then a relative progesterone deficiency may develop during the luteal phase of the cycle (luteal phase defect). Also, genetic or inherent problems with the egg can impact fertility.

About Me

Name: Dr. Eric Daiter

Location: United States

Dr. Daiter graduated medical school at Temple University Medical School in Philadelphia and completed the Obstetrics and Gynecology residency program at Albert Einstein College of Medicine in New York. He completed his Reproductive Endocrinology and Infertility fellowship at the Hospital of the University of Pennsylvania. He has considered a career as a physician scientist in research medicine and has published several articles on molecular events that occur during the human embryo's implantation into the uterus.